The present invention relates to the field of cathode ray tube manufacture. More particularly, the present invention relates to the field of salvaging components of a cathode ray tube that has failed preliminary testing and must have a component or components, particularly the electron gun, removed for analysis or replacement. The present invention provides a method of salvaging the remainder of the cathode ray tube, replacing the neck of the tube and reusing the reworked tube in completing the manufacture of a working unit.
Cathode ray tubes (xe2x80x9cCRTsxe2x80x9d) are used in most television sets and computer and video monitors. A cathode ray tube, on which the present invention can be practiced, is illustrated in FIG. 1. The CRT (100) is a glass tube with a bottle-like shape in which a relatively wide bell-like portion (101) narrows into an elongated neck portion (106).
At the wide end of the bell-like portion (101) is a relatively flat portion (102) of the CRT (100). This flat portion (102) becomes the screen on which the display of the television set or monitor is generated when the CRT is incorporated therein.
The flat or display portion (102) is typically sealed to the bell-like portion (101) using molten glass called frit (103). When the frit (103) cools and hardens, it seals the display surface (102) to the rest of the tube (100).
A layer of phosphor (105), a material that emits light when struck by an electron beam, is coated over the display portion (102) of the CRT. An electron gun (104) is then installed in the neck (106) of the CRT (100). A stream of electrons emitted from the electron gun (106) is scanned over the phosphor (105) and turned on and off during the scanning to cause the phosphor (105) to glow in certain places and not others. In very simple terms, this is how an image is generated on the screen (102) of a television or video monitor.
A electromagnetic yoke (not shown) is provided around the neck (106) of the CRT (100). This yoke produces a controlled magnetic field through which the electron beam from the electron gun (106) passes. The electron beam is deflected from a straight line by the magnetic field of the yoke. The degree and direction of the deflection depend upon the magnetic field generated by the yoke. Consequently, by varying the magnetic field created by the yoke in a precise cycle, the electron beam can be scanned, line-by-line, over the entire surface of the screen (102) to generate video images thereon.
When manufacturing a CRT, the installation of the electron gun (104) is a very important part of the process. Without an appropriately mounted and functioning electron gun (104), the CRT (100) will be useless. Consequently, the installation of the electron gun (104) is typically done with appropriate care. Additionally, it is important to prevent any dust or other contaminants from entering the tube (100) prior to installation of the electron gun (104). Once installed, the gun (104) is permanently sealed into the neck (106) of the tube (100).
After the gun (104) has been installed, it is tested to ensure that it will operate properly when the CRT (100) is completed and incorporated into a television set or video monitor. Unfortunately, it is not uncommon for the electron gun (104) to fail this testing.
Because the electron gun (104) is permanently sealed into the neck of the cathode ray tube (101), it has been the exclusive practice in the industry to destroy the tube (101) when an electron gun (104) has failed testing. The gun (104) may then be salvaged and tested to determine the cause of its failure. However, the CRT (101) is lost at considerable expense to the manufacturing process. It is estimated that the value of each such CRT (101) destroyed is $300 to $500.
Consequently, there is a need in the art for a means and method of salvaging more of the cathode ray tube when the electron gun has failed testing and must be removed for analysis and replacement.
The present invention meets the above-described needs and others. Specifically, the present invention provides a means and method of salvaging more of the cathode ray tube when the electron gun has failed testing and must be removed for analysis and replacement.
Additional advantages and novel features of the invention will be set forth in the description which follows or may be learned by those skilled in the art through reading these materials or practicing the invention. The advantages of the invention may be achieved through the means recited in the attached claims.
The present invention may be embodied and described as an improved and cost-efficient method of manufacturing cathode ray tubes, where an electron gun has been installed in a neck portion of a cathode ray tube and has failed testing. The method of the present invention includes removing the electron tube out of the neck portion of the cathode ray tube without damaging any portion of the cathode ray tube other than the neck portion; and forming a new neck portion on the cathode ray tube.
A second electron gun may then be installed in the newly-formed neck portion of the cathode ray tube. Preferably, the method also includes further testing of this second electron gun for operation within predefined parameters. The method may also preferably include testing the electron gun removed from the cathode ray tube to determine cause or extent of failure.
Removing the electron gun may be performed by cutting the electron gun out of the neck portion of the cathode ray tube. Alternatively, removing the electron gun may be performed by fracturing the neck portion of the cathode ray tube.
The method of the present invention may also include the initial testing of electron gun to determine a failure prior to removal of the electron gun. This testing preferably is performed by providing a signal to the electron gun to cause the electron gun to emit an electron beam; and monitoring output of the electron gun to determine operability of the electron gun according to predefined parameters.
The present invention also encompasses the necessary collection of devices and apparatuses required to perform the method described above. Specifically, the present invention encompasses a system of manufacturing cathode ray tubes, where an electron gun has been installed in a neck portion of a cathode ray tube and has failed testing. This system preferably includes means for removing the electron tube out of the neck portion of the cathode ray tube without damaging any portion of the cathode ray tube other than the neck portion; and means for forming a new neck portion on the cathode ray tube.